Trigger name in server actions does not show all the signals

Binary package hint: openerp-server

The dropdown list "trigger name" in "Server Actions" form view doesn't show all the available signals of the system.

This is the original code, it seems ther is a bug in the query
    def _select_signals(self, cr, uid, context={}):
        cr.execute("select distinct t.signal as key, t.signal || ' - [ ' || w.osv || ' ] ' as val from wkf w, wkf_activity a, wkf_transition t "\
                        " where w.id = a.wkf_id " \
                        " and t.act_from = a.wkf_id " \
                        " or t.act_to = a.wkf_id and t.signal not in (null, NULL)")
...
        return res

The right version should be
        cr.execute("select distinct t.signal as key, t.signal || ' - [ ' || w.osv || ' ] ' as val from wkf w, wkf_activity a, wkf_transition t "\
                        " where w.id = a.wkf_id " \
                        " and t.act_from = a.id " \
                        " or t.act_to = a.id and t.signal not in (null, NULL)")

I'm using openerp server version 5.0.5 in linux downloaded from Openerp.com

Regards.